Conversion of asphaltene-containing hydrocarbonaceous charge stocks

ABSTRACT

A COMBINATION PROCESS FOR EFFECTING THE CONVERSION OF ASPHALTENE-CONTAINING BLACK OILS. THE CHARGE STOCK, IN ADMIXTURE WITH NON-STOICHIOMETRIC VANADIUM SULFIDE, AND UNREACTED ASPHALTENES, IS INITIALLY SUBJECTED TO SOLVENT DEASPHALTING TO PROVIDE A SOLVENT-LEAN MIXTURE OF THE   VANADIUM SULFIDE AND THE PRECIPITATED ASPHALTENES. THIS MIXTURE IS SUBSEQUENTLY REACTED WITH HYDROGEN TO CONVERT THE ASPHALTENES INTO LOWER-BOILING HYDROCARBON PRODUCTS.

lUnited States Patent O 3,723,294 CONVERSION OF ASPHALTENE-CONTAININGHYDROCARBONACEOUS CHARGE STOCKS John G. Gatsis, Des Plaines, and WilliamK. T. Gleim,

Island Lake, Ill., assignors to Universal Oil Products Company, DesPlaines, Ill.

Filed Oct. 1S, 1971, Ser. No. 190,021 Int. Cl. Cg 37/00 U.S. Cl. 208-8610 Claims ABSTRACT OF THE DISCLOSURE A combination process for effectingthe conversion of asphaltene-containing black oils. The charge stock, inadmixture with non-stoichiometric vanadium sulfide, and unreactedasphaltenes, is initially subjected to solvent deasphalting to provide asolvent-lean mixture of the vanadium sulfide and the precipitatedasphaltenes. This mixture is subsequently reacted with hydrogen toconvert the asphaltenes into lower-boiling hydrocarbon products.

APPLICABILITY OF INVENTION The invention herein described is adaptableto a process for the conversion of asphaltene-containinghydrocarbonaceous charge stocks generally derived from various petroleumcrude oils. More specifically, the present invention is directed towarda slurry-type catalytic process for continuously converting atmospherictower bottoms products, vacuum tower bottoms products (vacuum residuum)crude oil residuum, topped crude oils, coal oil extracts, crude oilextracted from tar sands, etc. Such heavy hydrocarbonaceou's mixturesare referred to in the art as black oils.

Black o-ils contain high molecular weight sulfurous compounds inexceedingly large quantities and, in addition, excessive amounts ofnitrogenous compounds, high molecular weight organometallic complexes,principally comprising nickel and vanadium, and asphaltic material(asphaltenes). Asphaltic material is generally found to be complexed orlinked with sulfur and, to a certain extent, with the organometalliccompounds. The asphaltic material is concentrated in that fraction ofthe black oil having a normal boiling point above about 1050 F. Anabundant supply of such hydrocarbonaceous material exists, most of whichhas a gravity less than about 20.0 APl; a significant quantity has afgra'vity =less than about 10.0 API. Furthermore, black oils aregenerally characterized by a boiling range indicating that at least10.0% by volume has a normal boiling point above a temperature of about1050 F.

The process of the present invention is a combination process which isparticularly directed toward the conversion of black oils intodistillable hydrocarbon products. Specific examples of those black oils,illustrative of those to which the present invention is especiallyapplicable, include a vacuum tower bottoms product having a gravity of7.1 API, containing 4.05% by weight of sulfur and 23.7% by weight ofasphaltenes; and, a vacuum residuum having a gravity of 8.8 API,containing 3.0% by weight of sulfur, 4,300 p.p.m. of nitrogen and havinga 20.0% volumetric distillation `temperature of 1055 F. Through theutilization of the present invention, the conversion of the majority ofsuch material is afforded; such conversion has heretofore been believedvirtually impossible. Additionally, the process of the present inventionresults in a lower rate of catalyst deactivation and to the extent thatthe process may be conducted effectively for an extended period of time.The principal difficulty, heretofore experienced, resides in the lack ofa technique which affords many catalytic composites an acceptable degreeICC of sulfur stability while simultaneously producing lower boilingproducts from the asphaltic material. It is generally conceded that manyfixed-bed catalytic processes are available which can processhigh-boiling sulfurous charge stocks such as heavy vacuum gas oils.These processes fall far short, however, of economical operability whenprocessing asphaltene-containing material.

OBJECTS AND EMBODIMENTS One object of the present invention is toiprovide a more efficient process for the hydrogenative conversion ofheavy hydrocarbonaceous material containing asphaltics. A corollaryobjective is to increase the effective life of the catalytic compositeutilized in the conversion of asphaltene-containing charge stocks.Another objective is to convert yhydrocarbon-insoluble asphaltenes intohydrocarbon-soluble, lower-boiling normally liquid products.

A spcific object is tor effect the continuous decontamination ofasphaltenic black oils by providing a combination process utilizing asolid, unsupported catalyst, in which process there is afforded adecrease in the rate of catalyst deactivation.

Therefore, in one embodiment, the present invention is directed toward aprocess for the conversion of an asphaltene-containing hydrocarbonaceouscharge stock which process comprises the 'steps of: (a) deasphaltingsaid charge stock, in admixture with non-stoichiometric vanadiumsulfide, with a selective solvent in a solvent extraction zone toprovide (l) a solvent-rich, normally liquid phase and (2) a solvent-leanmixture of said non-stoichiometric vanadium sulfide and asphaltene's;and, (b) reacting said solvent-lean mixture with hydrogen, in aconversion zone, at conversion conditions selected to convert insolubleasphaltenes into lower-boiling hydrocarbon products.

In another embodiment, the resulting conversion zone effluent,containing the non-stoichiometric vanadium sulfide catalyst in admixturewith asphaltenes, is introduced into said solvent extraction zone.

Other embodiments of our invention relate primarily to operatingconditions and the use of selected solvents within the solventextraction zone. In one such embodiment, the charge stock is admixedwith non-stoichiometric vanadium sulfide in an amount of at elast 1.5%by weight, calculated as elemental vanadium; the preferred upper limit,for the concentration of non-stoichio metric vanadium sulfide, is about25.0% by Weight.

PRIOR ART The basic concept involved with the use of unsupported,non-stoichiometric vanadium sulfide as the catalytic agent for theconversion of hydrocarbonaceous black oils, is found in U.S. Pat. No.3,558,474 (Class 208-108). As indicated in the teachings of -thispatent, we found that non-stoichiometric vanadium sulfide exhibits anunusual degree of activity with respect to asphaltene conversion, whilesimultaneously eliminating a significant amount of the sulfurous andnitrogenous compounds. With respect to the present combination process,it should be noted that there exists, in the teachings of this portionof the prior art, no mention of solvent deasphalting, or extraction.

It must necessarily be acknowledged that the prior art is replete with awide spectrum of techniques for effecting the solvent deasphalting ofasphaltene-containing hydrocarbonaceous charge stocks. In the interestof brevity, no attempt will be made herein to tabulate exhaustively thesolvent deasphalting art.

Exemplary of such prior art is U.S. Pat. No. 1,948,296 (Class 2084) inwhich a combination process is described wherein the separated asphalticfraction is admixed with an oil and subjected to oxidation to obtain aparticularly good asphalt. The described solvents, for use inprecipitating the asphaltic fraction, include light petroleumhydrocarbons such as naphtha, casinghead gasoline, light petroleumfractions composed of propane, butane and isobutane, certain alcohols,ether and mixtures thereof, acetone, etc.

U.S. Pat. No. 2,002,004 (Class 208-14) involves a twostage deasphaltingprocess wherein the second stage completes the precipitation of asphaltswhich was partially effected in the first stage. As noted previously,the solvents described include naphtha, gasoline, casinghead gasolineand liquefied normally gaseous hydrocarbons such as ethane, propane,butane and mixtures thereof.

IU.S. Pat. No. 2,914,457 (Class 208-79) describes a multiple combinationprocess involving fractionation, vacuum distillationn, solventdeasphalting, hydrogenation and catalytic reforming. Again the suitableliquid deasphalting solvents include liquefied normally gaseoushydrocarbons such as propane, n-butane, isobutane, or mixtures thereof,as well as ethane, ethylene, propylene, n-bptylene, isobutylene,pentane, isopentane, and mixtures thereof.

While the foregoing examples of the deasphalting art serve to indicatethe now ancient use of a wide variety of deasphalting solvents, it mustbe noted that there is no indication of the present combination processwherein the charge stock, in admixture with a finely-divided,nonstoichiometric vanadium sulfide catalyst, is subjected to thedeasphalting operation. Furthermore, the prior art appears to be void ofany intent to effect asphaltic conversion to lower-boiling hydrocarbonproducts.

Mention should be made of U.S. Pat. No. 2,975,121 (Class 208-251)wherein the charge stock is initially subjected to h'ydrogenativecracking, followed by solvent deasphalting of the hydrogen-treated oilto remove suspended solid metal constituents. This reference indicatesthat the hydrogenation operation, for the initial treatment of themetal-containing charge oil, may be carried out in the presence of asuitable hydrogenation catalyst, and preferably one which issulfide-resistant. However, the only catalyst contemplated is nickeltungsten sulfide and cobalt molybdate. Furthermore, there is norecognition of the present combination process wherein the catalystcomposite is non-stoichiometric vanadium sulfide, the deasphaltingoperation produces a mixture of the vanadium sulfide with theprecipitated asphaltenes and the mixture is subjected to hydrogenativeconversion.

SUMMARY OF INVENTION As indicated in U.S. Pat. No. 3,558,474,unsupported vanadium sulfide catalyst, colloidally dispersed in thehydrocarbonaceous charge stock, has been found to be an effectivehydrorefining catalyst. The catalyst is nonstoichiometric, and isprepared in situ from the catalyst precursor, vanadium tetrasulfide. Theindicated procedure is to disperese finely-divided vanadium tetrasulfidein the charge stock, thermally decomposing the same in the presence ofhydrogen to yield the non-stoichiometric vanadium catalyst. We havefound that, when the catalyst is separated from the product effluentincluding unreacted asphaltenes and heavy oil, and rerun with additionalcharge stock, a marked decrease in catalyst activity takes place.

Unsupported, non-stoichiometric vanadium sulfide catalyst has little, ifany, internal surface area, and, therefore, the desired reactions mustbe effected on the external surface. As a consequence, the activity ofthe catalyst is principally dependent upon particle size. A high degreeof catalytic actiivty is initially obtained when the catalyst is formedfrom the catalyst precursor, vanadium tetrasulde. The finely-dispersedvanadium tetrasulfide breaks down into even smaller particles Whenthermally decomposed in the presence of hydrogen. The present inventiveconcept is founded upon recognition of the fact that,

as the catalyst precursor is thermally decomposed in the presence ofhydrogen and asphaltenes, the resulting nonstoichiometric vanadiumsulfide particles become associated with the asphaltenes and the latterserve to keep the catalyst colloidally dispersed. High catalyticactivity can be maintained provided the catalyst particles are notpermitted to agglomerate which is the case when the once-used catalystis rerun to combine with additional charge stock.

Where a high asphaltene conversion is obtained, resulting in aninsufficient quantity of asphaltenes to associate with the vanadiumsulfide catalyst particles, or if the catalyst is separated from theliquid product in a manner which removes the catalyst from anyasphaltenes associated with it, the catalyst particle will subsequentlyagglomerate resulting in a loss of external surface and, consequently, adecrease in catalytic activity. If, on the other hand, a too lowasphaltene conversion is obtained, leading to coke deposition on thecatalyst from the thermal decomposition of asphaltenes, or if thecatalyst is separated from the liquid product in a manner such thatcarbonization of the catalyst is effected, a similar decrease incatalytic activity results.

We have found that the activity of the non-stoichiometric vanadiumsulfide catalyst, when it is re-used with fresh hydrocarbonaceous blackoil, can be maintained close to the same level as when the catalyst isinitially formed from the catalyst precursor, vanadium tetrasulfide.This is accomplished by subjecting a mixture of the vanadium sulfidecatalyst and the hydrocarbonaceous charge stock, to a solventdeasphalting operation such that the catalyst particles appear in theheavy phase containing the asphaltenes and heavy oil constituents. Thisheavy phase is then subjected to conversion in the presence of hydrogenwith the result that lower-boiling hydrocarbon products are producedfrom the asphaltenes and heavy oils. Following separation of thehydrogen, from the conversion zone efiiuent, the remainder of theeffluent including unreacted asphaltenes and the vanadium sulfidecatalyst is introduced into the solvent extraction zone. As the processcontinues in operation, 100.0% by weight of the virgin asphaltenes willbe converted; however, this is not to be construed as stating that100.0% by weight of all the asphaltenes entering the conversion zone areso converted. In this manner, the non-stoichiometric vanadium sulfidecatalyst is constantly maintained in intimate association withasphaltenes, and, therefore, remains colloidally dispersed. There thenexists no tendency of the finely-divided vanadium sulfide catalyst toform large agglomerates which inherently lead to a decline in catalystactivity.

The concentration of non-stoichiometric vanadium sulfide, within theheavy phase recovered from the solvent extraction zone, is at leastabout 1.5% by weight, calculated on the basis of elemental vanadium.Excessive concentrations do not appear to enhance the overall result,even with extremely contaminated charge stocks exhibiting a highasphaltene content. Therefore, the upper limit of vanadium sulfide isabout 25.0% by weight. The charge stock/non-stoichiometric vanadiumsulfide mixture is introduced into an upper portion of a solventdeasphalting zone, wherein it countercurrently contacts a suitableselective solvent which is introduced into a lower portion thereof. Thesolvent deasphalting zone will function at a temperature in the range ofabout 50 F. to about 500 F., and preferably from about 100 F. to about300 F.; the pressure will be maintained within the range of about toabout 1,000 p.s.i.g., and preferably from about 200 to about 600p.s.i.g. The precise operating conditions will generally depend upon thephysical characteristics of the charge stock as well as the selectedsolvent. In general, the temperature and pressure are selected tomaintain the deasphalting operation in liquid phase, and to insure thatall the catalyst particles are removed in the solvent-lean heavy phase.

Suitable solvents include those hereinbefore described in the discussionof the prior art. Thus, it is contemplated that the solvent will beselected from the group of light hydrocarbons such as ethane, methane,propane, butane, isobutane, pentane, isopentane, neopentane, hexane,isohexane, heptane, etc. Similarly, the solvent may be a normally liquidnaphtha fraction containing hydrocarbons having from about to about 14carbon atoms per molecule, and preferably a naphtha fraction having anend boiling point below about 200 F. The solvent-rich normally liquidphase is introduced into a suitable solvent recovery system, the designand techniques of which are thoroughly described in the prior art.

The solvent-lean heavy phase, from the deasphalting zone, containing thevanadium sulfide catalyst, asphaltenes and heavy oil constituents, isadmixed with hydrogen in an amount above about 5,000 s.c.f./bbl. Thepractical upper limit for hydrogen concentration is about 50,- 000s.c.f./bbl. Following suitable heat-exchange with various hot efuentstreams, the temperature of the mixture is further increased to thelevel desired at the inlet to the reaction zone. Since the reactionsbeing effected are principally exothermic in nature, the temperature ofthe efiiuent from the reaction Zone will be considerably higher than theinlet temperature. Therefore, the inlet temperature will be controlledin the range of about 325 C. to about 400 C. The residence time in thereaction zone is such that the efiiuent temperature is not substantiallyhigher than about 500 C. Although suitable results are obtained at amaximum reaction temperature of 5 00 C., a preferred mode of operationlimits the maximum reaction temperature to about 450 C. The reactionzone will be maintained under an imposed pressure of about 500 to about5,000 p.s.i.g.

Although the present process may be effected in an elongated reactionzone with the slurry and hydrogen being introduced into the upperportion thereof, the effluent being removed from a lower portion, anupffow system offers advantages. One principal advantage resides in thefact that the extremely heavy portion of the charge stock, particularlythat portion boiling above a temperature of about 1050 F., will have anappreciably longer residence time within the reaction zone, with theresult that a greater degree of conversion thereof becomes attainable.

The product efiiuent, including the vanadium sulfide catalyst andunreacted asphaltenes, is introduced into a suitable separation systemfrom which a hydrogen-rich gaseous phase is recovered for purposes ofrecycle to combine with the material being introduced into the reactionzone. The hydrogen separation system is not considered an essentialfeature of the present combination process, and may consist of one ormore suitably operated vessels from which the hydrogen is recovered;other normally gaseous streams may be separately recovered, including,for example, a methane/ethane concentrate and a propane/butaneconcentrate. The remainder of the product effluent is introduced intothe upper portion of the solvent deasphalting zone.

The conversion of hydrocarbonaceous black oils appears to bebeneficially affected when carried out in the presence of hydrogensulfide. Therefore, it is within the scope of the present invention thatfrom about 2.50 to about 25.0 mol percent hydrogen sulfide will bepresent in the hydrogen entering the conversion reaction zone.

DESCRIPTION OF DRAWING One embodiment of the present invention ispresented in the accompanying drawing by means of a simplified flowdiagram in which details such as pumps, instrumentation and controls,heat-exchange and heat-recovery circuits, valving, start-up lines andsimilar hardware have been omitted as not essential to an understandingof the techniques involved. The utilization of such miscellaneousappurtenances, to modify the illustrated process flow, is well withinthe purview of those skilled in the art.

With reference now to the drawing, the charge stock in line 1 is admixedwith a mixture of non-stoichiometric vanadium sulfide and unreactedasphaltenes in line 2, the mixture continuing through line 1 intodeasphalting zone 3. A selected solvent, for example a mixture ofisobutane and n-butane, is introduced into a lower portion ofdeasphalting zone 3 by way of line 4, and is inclusive of make-upsolvent from line 5. The solvent-rich, normally liquid hydrocarbon phaseis removed through line 6, and introduced thereby into a suitablesolvent recovery system 7. The isobutane/n-butane solvent is recycledthrough line 4, while the normally liquid product of the process isremoved by way of line 8.

The solvent-lean mixture of non-stoichiometric vana-A dium sulfide,precipitated asphaltenes and high-boiling heavy oil components, iswithdrawn from deasphalting zone 3 by way of line 9 and introduced intothe lower portion of reaction zone 12. The product effluent is withdrawnthrough line 13, and introduced into hydrogen separation system 14, fromwhich a hydrogen-rich recycle gas stream is recovered in line 10 andrecycled, along with make-up hydrogen from line 11, to combine with thecharge to the reaction zone in line 9. The non-stoichiometric vanadiumsulfide, unreacted asphaltenes, and the normally liquid productefiiuent, for example hexaneplus, is removed from hydrogen separationsystem 14 through line 2, and is introduced by way of line 1 intodeasphalting zone 3. In order to prevent undue metals build-up withinthe system, a drag stream is withdrawn through line 15 and sent to asuitable metals recovery facility.

It will be noted, from the flow just described, that thenon-stoichiometric vanadium sulfide is constantly maintained in intimateassociation with asphaltenes. Thus, there is afforded a significantdecrease in the rate of catalyst deactivation as indicated by analysesof the product in line 8. Being devoid of metalic contaminants and highmolecular weight asphaltenes, the product in line 8 is suitable fordirect utilization as the charge stock to a fixedbed system for completeremoval of the remaining sulfurous and nitrogenous compounds.Furthermore, since the charge stock/vanadium sulfide mixture isinitially subjected to a deasphalting technique, the size of thesubsequent reaction zone will be significantly decreased.

EXAMPLES The following examples are presented for the sole purpose ofillustrating the process of the present invention, and it is notintended that the invention be limited to the specifics involved. Thehydrocarbonaceous charge stock employed was a vacuum column bottomsproduct having a gravity of 6.2" API, an initial boiling point of 546 F.and a 10.0% volumetric distillation temperature of 958 F.; 24.0% byvolume was distillable at a temperature of 1050 F. The charge stockcontained 13.3% by weight of asphaltenes, 4.88% by weight of sulfur,0.48% by weight of nitrogen, 400 p.p.m. of vanadium and 70 p.p.m. ofnickel, the latter existing as organometallic porphyrins.

Example I In this example, the charge stock was employed in an amount of200 grams per hour, and was admixed with 18.9 s.c.f./hour of hydrogen(15,000 s.c.f./bbl.); the mol percent hydrogen sulfide in the recyclegas was 17.0. The reaction zone was maintained at a pressure of 3,000p.s.i.g. and a peak (maximum) reaction zone temperature of 443 C. Thenormally liquid portion .of the product efiiuent was subjected tosolvent deasphalting, utilizing propane, at a temperature of 67 C. and apressure suflicient to maintain the deasphalting operation in liquidphase.

The catalyst was first employed in an amount of about 3.2% by weight forthe conversion of a topped crude oil having a gravity of 8.0 API. Thecrude contained 10.53%

7 by weight of asphaltenes, 2.80% by weight of sulfur and 578 ppm. ofmetals. The non-stoichiometric vanadium sulfide catalyst was rerun twicefollowing removal of all the benzene-soluble material and asphaltenes.Results of this operation are presented in the following Table I:

TABLE I.-TOPPED CRUDE PROCESSING Gravity, Sulfur,

Run number API Asphaltics Wt. percent Catalyst deactivation is readilyapparent from the foregoing tabulation; by the time of the second rerun(run No. 3) the gravity had decreased to 16.7 and the residualasphaltics had increased to 2.40% by weight.

At this point, the charge stock was changed to the vacuum column bottomspreviously described. Again the vanadium sulde catalyst, in theincreased amount of about 7.9% by weight, was rerun (four times)following removal of the benzene-soluble material and the residualasphaltenes. In the following Table Il there are presented the resultsof the last three catalyst rerun operations.

TABLE Ill-VACUUM BOTTOMS PROCESSING Gravity, Sulfur,

Run number API Asphaltics wt. percent Catalyst deactivation isparticularly noticeable with respect to the residual asphalticsconcentration; with fresh catalyst, more than 99.0% of the virginasphaltenes were converted, while the above figures indicate only about87.0% asphaltene conversion.

Example II In accordance with the present invention, the chargestock/vanadium suliide slurry is admixed with unreacted asphaltenes, andsubjected to a n-butane deasphalting operation at a temperature of about70 C. and a pressure sufficient to maintain the operation in liquidphase. Approximately 20.0% by volume of the original charge stock isremoved in a solvent-rich phase and introduced into a suitable solventrecovery system. The remaining heavy oil constituents,non-stoichiometric vanadium sulfide, in an amount of about 3.0% byweight, and precipitated asphaltenes are introduced into the lowerportion of a reaction zone maintained at a maximum temperature of about425 C. and under an imposed pressure of about 3,000 p.s.i.g. The chargeis admixed with a hydrogen-rich gas in an amount of about 17,000s.c.f./bbl., containing about 15.0 mol percent of hydrogen sulfide.

Following separation of the reaction product eiuent, to concentrate thehydrogen for recycle to the reaction zone, the remainder is admixed withfresh hydrocarbon charge stock and introduced into the solventdeasphalting zone. After a period of about 100 hours, approximately10.0% of the reaction product eiuent is withdrawn and, following removalof hydrocarbon-soluble products, is sent to a metals recovery system.

Analyses of the normally liquid product eflluent including thatrecovered from the drag stream when applicable, indicate a recovery ofthe initial catalyst activity. At about fifty hours of operation, theresidual asphaltene concentration is about 1.25%; at 142 hours, it hasdropped to about 0.50%; at hours, the residual asphaltics amount toabout 0.25%; and, after about 200 hours, the concentration is about0.10%.

The foregoing clearly indicates the method by which the presentinvention is effected and the benefits to be afforded through theutilization thereof.

We claim as our invention:

1. A process for the conversion of an asphaltene-con taininghydrocarbonaceous charge stock which comprises the steps of (a)deasphalting said charge stock, in admixture with non-stoichiometricvanadium sulfide, with a selective solvent in a solvent extraction zoneto provide (l) a solvent-rich, normally liquid phase and (2) asolvent-lean mixture of said non stoichiometric vanadium sulfide andasphaltenes; and,

(b) reacting said solvent-lean mixture with hydrogen,

in a conversion zone, at conversion conditions selected to convertinsoluble asphaltenes into lowerboiling hydrocarbon products.

2. The process of claim 1 further characterized in that the resultingconversion zone eiuent is introduced into said solvent extraction zone.

3. The process of claim 1 further characterized in that said conversionconditions include a temperature from about 300 C. to about 500 C. and apressure in the range of about 500 p.s.i.g. to about 5,000 p.s.i.g.

4. The process of claim 1 further characterized in that said chargestock is admixed with non-stoichiometric vanadium sulfide in an amountof at least 1.5% by weight, calculated as elemental vanadium.

5. The process of claim 1 further characterized in that the hydrogenconcentration, in said conversion zone, is at least about 5,000s.c.f./bbl.

6. The process of claim 1 further characterized in that said selectivesolvent is a light hydrocarbon containing from one to about seven carbonatoms.

7. The process of claim 1 further characterized in that said selectivesolvent is a normally liquid naphtha fraction containing hydrocarbonshaving from about five to about fourteen carbon atoms per molecule.

8. The process of claim 1 further characterized in that the volume ratioof said selective solvent to said charge stock is from about 3:1 toabout 15:1.

9. The process of claim 6 further characterized in that said selectivesolvent comprises n-butane.

10. The process of claim 7 further characterized in that said naphthafraction has an end boiling point below about 200 F.

References Cited UNITED STATES PATENTS 7/1951 Douce 208--86 1/1971 Gleimet al. 208-108 HERBERT LEVINE, Primary Examiner

